Principles of physics 1 final test for the 1 st semester 2019 2020

At the end of the time interval, the kinetic energy of the cart of mass m is A.. one fourth of the kinetic energy of the cart with mass 2m.. one half the kinetic energy of the cart with

FACULTY OF APPLIED SCIENCE

FINAL TEST FOR THE 1 st SEMESTER

Academic Year: 2019-2020

Subject: Principles of Physics 1

Date: January 6 th 2020

Course number: PHYS130902E

Test number: 01 (2 pages)

Duration: 90 minutes

Note:

+ Students are allowed to use one A4 double-sided paper sheet of handwritten notes

+ Invigilators are NOT allowed to explain anything related to the contents of the test

+ The value of gravitational acceleration is g=9.80 m/s2 when needed

letter A, B, C, D, or E related to your choice(s) on

your answer sheet

Question 1 (0.5 marks)

The graph shows the position as a function of time for two

trains running on parallel tracks For times greater than t

=0,

which of the following is true:

A At time tB, both trains have the same instantaneous

velocity

B The speed of both trains increases all the time

C Both trains have the same instantaneous velocity at some

time before tB

D Somewhere on the graph, the velocities of both trains are

changing in the same way

Two carts of masses m and 2m are at rest on a horizontal

and frictionless surface Both carts are

pushed with equal forces for the same time interval At the end of the time interval, the kinetic

energy of the cart of mass m is

A one fourth of the kinetic energy of the cart with mass

2m

B one half the kinetic energy of the cart with mass 2m

C equal to the kinetic energy of the cart with mass 2m

D twice the kinetic energy of the cart with mass 2m

E four times the kinetic energy of the cart with mass 2m.

Question 3 (0.5 marks)

As a particle moves in the positive x-direction with a

constant momentum,

the magnitude of the angular momentum about the point

S (the origin):

A decreases and then increases

B increases and then decreases

C is constant

D is zero because this is not circular motion

A Carnot heat engine runs between a cold reservoir at

temperature Tc and a hot reservoir at

temperature Th You want to increase its efficiency Of

the following, which change results in

the greatest increase in efficiency? The value of ∆T is the

same for all changes

A Lower the temperature of the hot reservoir by ∆T

B Lower the temperature of the cold reservoir by ∆T

C Raise the temperature of the hot reservoir by ∆T

D Raise the temperature of the cold reservoir by ∆T

Question 5 (1.0 marks)

In a collision between two cars, which would you expect

to be more damaging to the occupants:

if the cars collide and remain together, or if the two cars collide and rebound backward?

Explain

Roofs of houses are sometimes “blown” off (or are they pushed off?) during a tornado or

hurricane Explain

Question 7 (2.0 marks)

A bullet of mass m1 traveling

horizontally with speed u hits a block

of mass m2 that is originally at rest

and becomes embedded in the block

After the collision, the block slides a

distance d horizontally on a surface

with friction , and then falls off the

surface at a height h, as shown The coefficient of kinetic

friction between the block and the

surface is μk Assume the collision is nearly

instantaneous, and all distances are large compared

to the size of the block Neglect air resistance.

a What is umin, the minimum speed of the bullet, so that

the block falls off the surface?

b Assume that the initial speed of the bullet u is large

enough for the block to fall off the

surface Calculate xf, the position where the block hits

the ground measured from the bottom

edge of the surface, in terms of some or all of the following: 𝑢, 𝑚1 , 𝑚2 , 𝜇𝑘, 𝑑, ℎ, 𝑔

Question 8 (2.0 marks)

a moment of inertia 1 2 𝑚𝑝𝑅 2 The pulley is free to rotate about a frictionless pivot at its center A

massless string is wound around the pulley and

the other end of the rope is attached to a block of

mass m that is initially held at rest on frictionless

inclined plane that is inclined at an angle β with respect

to the horizontal The downward

acceleration of gravity is g The block is released from

rest How long does it take the block to

move a distance d down the inclined plane?

Question 9 (2.0 marks)

Consider the following two-step process Heat is allowed

to

flow out of an ideal gas at constant volume so that its pressure

constant

pressure, from a volume of 5.9 L to 9.3 L, where the

temperature reaches its original value Calculate

(a) the total work done by the gas in the process,

(b) the change in internal energy of the gas in the process, and

(c) the total heat flow into or out of the gas

1 atm = 1.01 × 105Pa=1.01 × 105N/m2

C When the tangent line to the curve of train 1 is

parallel to the line of train 2

CÂU 2

CÂU 3

C 𝐿 = 𝑝𝑑 = 𝑐𝑜𝑛𝑠𝑡 The distance from the origin to

the direction of p is unchanged.

C 𝐿 = 𝑝𝑑 = 𝑐𝑜𝑛𝑠𝑡 The distance from the origin to

the direction of p is unchanged.

CÂU 4

CÂU 5

The collision in which the two cars rebound would probably be more damaging In

the case of the cars rebounding, the change in momentum of each car is greater than

in the case in which they stick together because each car

is not only brought to rest but

also sent back in the direction from which it came A

greater impulse results from a

greater force, and so most likely more damage would

occur

During a hurricane or tornado, the outside air pressure may drop suddenly because of

the high wind speeds, as shown by Bernoulli’s principle The greater air pressure

inside the house may then push the roof off.

CÂU 7

Method 2:We can use Newton’s equations to find the

acceleration and find the time

a 𝑊 the total work done on the gas in the process:= 𝑊

The work done by the gas is 480J

b the change in internal energy of the gas in the process, and

∆𝐸𝑎𝑏𝑐 = Δ𝐸𝑎𝑐 = 0

Because the internal energy is a state variablel and depends only on the temperature

c the total heat flow into or out of the gas